Most insulins are OK for several weeks at up to 25 deg C. As westlakes said, don't freeze it by placing ice against it. I don't bother with any special precautions. The only place I've had problems was transiting Bangkok. How much insulin have you got? Why have you got this much (I'm away for a month) Why do you take insulin? (for fun! - why do you think?) How often do you take it? How much do you take? What flight did you arrive on? What flight are you leaving on? Why are they the same flight number?What is your passport number? Then, having got passport in hand, 'What is your name?'
I find BA's diabetic meals as OK as any other airline meal.